From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Wed, 20 Jun 2018 23:36:55 +0000 (+0000)
Subject: When a dependent alignas is applied to a non-dependent typedef,
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=fc8d6b0b1110ed2dfdf4c9196500306f84db6b3f;p=clang

When a dependent alignas is applied to a non-dependent typedef,
prioritize the error for the bad subject over the error for the
dependent / non-dependent mismatch.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@335191 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 779192b865..614432b0e2 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -3440,16 +3440,6 @@ static void handleAlignedAttr(Sema &S, Decl *D, const AttributeList &AL) {
   if (!AL.isPackExpansion() && S.DiagnoseUnexpandedParameterPack(E))
     return;
 
-  if (E->isValueDependent()) {
-    if (const auto *TND = dyn_cast<TypedefNameDecl>(D)) {
-      if (!TND->getUnderlyingType()->isDependentType()) {
-        S.Diag(AL.getLoc(), diag::err_alignment_dependent_typedef_name)
-            << E->getSourceRange();
-        return;
-      }
-    }
-  }
-
   S.AddAlignedAttr(AL.getRange(), D, E, AL.getAttributeSpellingListIndex(),
                    AL.isPackExpansion());
 }
@@ -3496,7 +3486,18 @@ void Sema::AddAlignedAttr(SourceRange AttrRange, Decl *D, Expr *E,
     }
   }
 
-  if (E->isTypeDependent() || E->isValueDependent()) {
+  if (E->isValueDependent()) {
+    // We can't support a dependent alignment on a non-dependent type,
+    // because we have no way to model that a type is "alignment-dependent"
+    // but not dependent in any other way.
+    if (const auto *TND = dyn_cast<TypedefNameDecl>(D)) {
+      if (!TND->getUnderlyingType()->isDependentType()) {
+        Diag(AttrLoc, diag::err_alignment_dependent_typedef_name)
+            << E->getSourceRange();
+        return;
+      }
+    }
+
     // Save dependent expressions in the AST to be instantiated.
     AlignedAttr *AA = ::new (Context) AlignedAttr(TmpAttr);
     AA->setPackExpansion(IsPackExpansion);
diff --git a/test/CXX/dcl.dcl/dcl.attr/dcl.align/p1.cpp b/test/CXX/dcl.dcl/dcl.attr/dcl.align/p1.cpp
new file mode 100644
index 0000000000..ec7b22f753
--- /dev/null
+++ b/test/CXX/dcl.dcl/dcl.attr/dcl.align/p1.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -std=c++11 -verify %s
+
+typedef int A alignas(4); // expected-error {{'alignas' attribute only applies to variables, data members and tag types}}
+template<int N> void f() {
+  typedef int B alignas(N); // expected-error {{'alignas' attribute only applies to variables, data members and tag types}}
+}